OStatic

All open-source licenses are not created equal. Understanding the different licenses is essential before you start to use, and modify, open-source code.

All open-source licenses have certain common elements: They promise that the source code may be used by anyone, for any purposes. They promise that the software may be changed by anyone, in any way that they like. And they promise that people who use the software never have to pay the authors or distributors.

Why are there so many licenses? And how do they differ?

For most people, the most important part of a software license is the end. That's because they're totally uninterested in the license itself; they are merely interested in scrolling past it, so that they can click on OK and install the software that they are running. For users of open-source software, however, licenses should be extremely important, because they determine what you may and may not do with a particular program. Open-source developers have long debated the merits of the GNU General Public License vs. the BSD License. As open-source software becomes mainstream, and is integrated into larger systems, these age-old arguments are less theoretical than ever, and should be understood not only by developers, but also by managers and executives of organizations working with open source. Van Lindberg's new book is an excellent place to start.

The developers of PHP announced last week that PHP version 4.4.9 is now available. This would not be remarkable in and of itself, except that the developers also indicated that this would be the last release of PHP 4.4. If PHP were commercial software, its end of life would be cause for panic in some quarters. The end of life of an open-source project works differently, of course. It does mean that the official development group will no longer spend time and energy fixing bugs in these old versions. But that's where the similarities between proprietary and open-source software ends.

The term open source was supposed to remove confusion, and was deliberately chosen to emphasize what the software is, rather than what it isn't. The good news is that when the term open source was coined, just 10 years ago, the world was ready to listen, and incorporated this term into its vocabulary. The bad news is that the open source world is now so diverse, with so many licenses and commercial interests involved, that it is often hard to know whether a program is truly available on an open source basis without reading the fine print.

The Software Freedom Law Center just announced its fourth victory over a software company that incorporated GPL-licensed software in its proprietary product. What happens when the SFLC sues a software company, and how can proprietary software vendors best work with the open-source world? The answer depends, as always, on the license.